Integral insole with multiple areas of different resiliency and method of making the insole

ABSTRACT

An insole for a shoe includes a body that is configured to fit within the shoe. A heel recess in a heel area of the insole extends partially through the body. A metatarsal opening in a metatarsal area of the insole extends completely through the body. A heel insert is secured in the heel recess, and a metatarsal insert is secured in the metatarsal opening. A method is disclosed for making an insole by mixing a reactive resin with a quantity of cork particles to form a body mixture. The mixture is injected into an injection mold to form a body portion of the insole that includes a heel recess and metatarsal opening. A heel insert and metatarsal insert are molded and provided in the heel recess and metatarsal opening, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional Application No. 61/245,701 filed Sep. 25, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to insoles for shoes that are inserted in a shoe on top of a built-in insole or would replace a removable insole of the shoe.

2. Background Art

Shoes are generally constructed to include a sole and a built-in insole that is either cemented onto the sole of the shoe, or is removable. Insoles are inserted into shoes on top of the built-in insole or may replace the removable insole to provide additional cushioning and support in the shoe. Persons who may benefit from inserts may include runners, athletes, diabetics, and the like.

Generally, insoles are formed in one piece of either foam or an elastomeric material. One example of a foam material commonly used in the manufacture of insoles is ethylene vinyl acetate (EVA) foam that uses air pockets formed in situ in the material to create a cushioning effect. One problem with this type of material is that the EVA foam lacks durability and breaks down with each step. Multiple piece insoles have also been developed that provide cushioning areas formed of different compositions.

The above problem and other problems are addressed by Applicants as summarized below.

SUMMARY OF THE INVENTION

An insole is disclosed that includes a plurality of different areas to provide stable support and increased resiliency in localized areas of the insole.

The insole includes a body portion that is molded from a mixture of polyurethane and granulated cork. The body portion defines a metatarsal opening that extends completely through the body portion. A soft medical grade silicone insert is assembled to the metatarsal opening to provide resiliency and comfort for the metatarsal portion of a wearer's foot. The body portion constrains and stabilizes the silicone insert. A heel area referred to as the heel pod is molded from an elastomer material below a heel area of the body portion. The heel pod does not extend through the body portion, but is attached in a layered arrangement. A fabric cover layer is bonded to the top surface of the body portion and is cut away when the metatarsal opening is cut into the body portion. An interchangeable or removable arch support may be attached to the body portion to permit the insole to be adapted for use by persons having various foot arch heights.

According to another aspect of the disclosure, an insole for a shoe is provided that comprises a body that is configured to fit within the shoe that defines a heel recess that extends partially through the body in a heel area and a metatarsal opening that extends completely through the body in a metatarsal area. A heel insert is secured in the heel recess and a metatarsal insert secured in the metatarsal opening.

According to another aspect of the disclosure, an insole for a shoe is provided that comprises a body having a bottom surface and a top surface defining a thickness. The body defines a heel recess that extends from the bottom surface and partially towards the top surface in a heel area. A metatarsal opening extends completely through the body in a metatarsal area. The metatarsal opening includes a metatarsal shoulder defined outboard the opening that has a depth less than the thickness of the body. A heel insert is secured to the heel recess, and a metatarsal insert is secured to the metatarsal opening and metatarsal shoulder.

According to other aspects of the disclosure, the body of the insole has a hardness of between 25 and 35 on the Shore A scale and the inserts have a hardness of less than 10 on the shore A scale. More specifically, the body of the insole may has a hardness of 30 on the Shore A scale and the inserts may have a hardness of 5 on the Shore A scale. The body of the insole may be formed of a mixture of polyurethane and cork particles. The inserts may be formed of medical grade silicone.

According to another aspect of the disclosure, the insole may further comprise an arch support attachment that is assembled to a lower surface of the body between the heel area and the metatarsal area. The arch support attachment may have a first surface feature and the body may have a second surface feature that cooperate to secure the arch support attachment to the body. The first surface feature may be a rib and the second surface feature may be a groove defined on a lower surface of the body.

According to further aspects that relate to the metatarsal opening, a metatarsal wall may be at least partially defined about the periphery of the metatarsal opening. The metatarsal opening wall extends from a top surface of the body to a bottom surface of the body. The metatarsal insert is adhered to the metatarsal opening wall. The metatarsal opening includes a metatarsal area shoulder defined outboard of the metatarsal opening that has a depth that is less than the thickness of the body in the metatarsal area. The metatarsal insert includes a step extending outwardly from the periphery of the metatarsal insert that is configured to adhere to the metatarsal area shoulder.

The heel recess includes a heel area shoulder defined outboard of a base area of the recess, that has a depth that is less than the depth of the base area. The heel recess extends from a bottom surface of the body and partially towards a top surface of the body.

The insole also may include a fabric layer that defines a cut-out portion and that is secured to the body with the cut-out portion being aligned with the metatarsal opening. The fabric layer may include a bamboo fiber. The fabric is adhered to a top surface of the body.

The insole may be a supplemental insole for a shoe that has an integral insole that is configured to fit within the shoe on top of an integral insole. Alternatively, the insole the shoe may have a removable insole and the insert may be configured to fit within the shoe to replace the removable insole.

An exemplary method of making the insole is summarized below. A clam shell injection mold having an upper portion that defines an upper mold cavity and a lower portion that defines a lower mold cavity may be used to manufacture the insole. A segment of fabric is pinned or otherwise attached to the upper portion of the mold spanning the upper mold cavity. An elastomeric material is injected into the heel pod forming portion of the lower mold cavity in the lower portion of the clam shell injection mold. A two-part reactive resin system is mixed with a quantity of granulated cork particles to form a body composition mixture. The body composition mixture is injected into the lower mold cavity and onto the elastomer in the heel pod portion. A molded interface is created between the heel pod elastomer and the body mixture composition above the heel pod. As the body composition mixture is injected, a metatarsal opening area is molded in the lower mold cavity. The segment of fabric is secured by laminate bonding to the top surface of the body portion. The metatarsal opening area and the fabric bonded to that area is trimmed to finish the metatarsal opening. A metatarsal insert is molded in the shape of the metatarsal opening in a separate molding operation. The metatarsal insert is then assembled to and bonded, or adhered, to the metatarsal opening.

According to another aspect of the method of making an insole, the method may be performed in an injection mold in which a first part and a second part of a reactive resin system is mixed with a quantity of cork particles to form a body mixture. The body mixture is injected into the injection mold and a body portion of the insole is molded to include a heel recess and a metatarsal opening area. A heel insert is molded from silicone in the shape of the heel recess. A metatarsal insert is molded from silicone in the shape of the metatarsal opening. The heel insert and metatarsal insert are attached to the heel recess and the metatarsal opening, respectively.

According to other aspects of the method, during the step of molding of the body portion a base and a heel wall are formed about the heel recess and a metatarsal wall is formed about the metatarsal opening. In addition, during the step of molding of the body portion, the heel insert is bonded to the base and the heel wall and during the step of attaching the metatarsal insert, the metatarsal insert is bonded to the metatarsal wall.

The method may be practiced in the injection mold that has an upper portion that defines an upper mold cavity and a lower portion that defines a lower mold cavity. The method may further comprise attaching a segment of fabric to the upper mold cavity wherein the segment of fabric is bonded to a top surface of the body portion. In addition, the segment of fabric may be trimmed to define an opening corresponding to the metatarsal opening in the body portion.

These and other aspects of the insole and method of making the insole developed by Applicants will be better understood in view of the attached drawings and the following detailed description of the illustrated embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of the bottom of a insole having multiple areas of different resiliency;

FIG. 2 is a top plan view of the insole shown in FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 3-3 in FIG. 2;

FIG. 4 is a bottom plan view of the insole without an arch support attached;

FIG. 5 is a bottom plan view of the insole with an arch support attached to the arch support cavity of the insole;

FIG. 6 is a perspective view of a small arch support insert; and

FIG. 7 is a perspective view of a large arch support insert.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to FIG. 1, a insole 10 is illustrated with its component parts separated from the insole 10. Insole 10 includes a body portion 12 that is formed of a mixture of polyurethane and granulated cork particles. It should be understood that the body portion may be formed from another mixture of material that offers similar resiliency and strength characteristics. The body portion 12 in the illustrated exemplary embodiment is made from a polyurethane foam or elastomer having a hardness in the range of 20 to 50 on the Shore A scale. More specifically, the hardness range may be between 25 and 36 on the Shore A scale with the optimum hardness believed to be about 30 on the Shore A scale. The polyurethane foam is a two-part polyurethane including polyol and isocyanate and a blowing agent that are blended with granulated cork particles that increase the hardness of the mixture after curing. The granulated cork particles are preferably 14/30 mesh granulated cork. The hardness of body portion 12 can be controlled by increasing the amount of cork added to the mixture. The cork is preferably 20% by weight of the mixture. The mixture is blended and then pumped to a mix head that injects the mixture into the mold.

The granulated cork particles have a honeycomb arrangement of cells that comprise complex fatty acids that are filled with compressed air-like gas. The granulated cork particles may be compressed to about half of their depth without losing flexibility. The cork particles also provide the unique ability to be compressed in one direction without increasing size in another direction. When the granulated cork particles are mixed with polyurethane, the cured mixture may be cut, shaped or shaved to the desired dimensions. In this way, the body portion 12 that is made from the cured mixture of polyurethane and granulated cork particles may be shaped to provide a customized insert that is adapted to the dimensions of a user's foot and to fit into a shoe.

The polyurethane base in the body portion 12 offers resiliency that provides energy return when compressed. Polyurethane is durable and resists permanent deformation after repeated compression to offer a user many years of comfort and support.

A metatarsal insert 16 is preferably made from silicone and is formed in an arcuate, or boomerang, shape to conform to the metatarsal and outer arch portion of a user's foot. The metatarsal insert 16 extends from the top to the bottom surface of the insert 10. The metatarsal insert 16 may be made of medical grade liquid silicone rubber. The hardness of the insert may range from 1 to 25 on the Shore A scale. More specifically, the silicone rubber may have a hardness of 1-9 on the Shore A scale and most preferably has a hardness of about 5 on the Shore A scale.

The inserts are intended to replicate the hardness of the natural fatty tissue on a young person's foot that sometimes diminishes with age. The silicone provides superior rebound resilience so that the metatarsal insert 16 returns to its original shape after compression. The silicone absorbs shock and displaces the energy away from the point of impact. The body portion 12 constrains the periphery of the metatarsal insert 16. The functional characteristics of the medical grade silicone are believed to offer more comfortable support of the metatarsal portion of a person's foot. The medical grade silicone is also less likely to cause irritation to the wearer's skin.

A heel pod 18 is preferably formed of an elastomer, such as polyurethane or silicone. The heel pod 18 may be made from polyurethane elastomer having a hardness in the range of 5 to 50 on the Shore A scale. More specifically, the hardness range may be between 5 and 25 on the Shore A scale with the optimum hardness being about 10 on the Shore A scale. The heel pod 18 may be made of an elastomer such as liquid polyurethane (non-foamed).

The heel pod 18 is provided below the rear part of the body portion 12. The cured polyurethane and cork mixture provides a durable heel landing area that benefits from a softer feel provided by the elastomer forming the heel pod 18. The insole 10 is preferably convex in shape to form a heel receiving area for a user's foot. The heel cup area cradles the heel of a user's foot aligning the natural shock absorbing pad under the heel bone of a user's foot with the heel pad 18. Optimal padding, including the natural shock absorbing pad and the insole should be at least 14 mm in depth to correctly pad and stabilize the heel during the striking phase of the human step.

A removable or replaceable arch support 20 is also shown in FIG. 1.

The removable arch support is preferably made of the same material as the body portion 12. That is, a cured polyurethane and granulated cork mixture. The functionality of the insole 12 may be improved by providing customized arch supports. Different arch supports may be provided to accommodate different heights and lengths of the arch of a user's foot. Arch supports must be easily assembled to the body portion 12 and secured by a durable securing mechanism. The arch support may be attached or adhered to the base of the insole in various ways. The preferred connection mechanism will be described with reference to FIGS. 4-7 below. Ideally, the arch support 20 is configured to conform, as closely as possible, to the natural arch of a user's foot.

A cover 22 is shown below the body portion 12 in FIG. 1, but it should be understood that the cover 22 is on the top of the insole 10 in use. The cover 22 extends across the full length and width of the insole 10 and is bonded or otherwise adhered to the upper surface of the body portion 12. The cover 22 may be a fabric selected to absorb and evaporate moisture quickly. The cover may be made of a moisture managing fabric that may be made of about 75% polyester and about 25% natural bamboo fibers. Bamboo or other similar natural material is preferred because of its natural anti-bacterial and anti-fungal properties that naturally neutralize odors. The fabric cover 22 must be flexible to allow it to conform and remain adhered to the different parts of the insole 10. A binder may be laminated to the fabric cover 22 to promote adhesion and sealing. The binder fabric may also function to prevent the polyurethane mixture from penetrating through the fabric cover 22 during manufacture or use.

A metatarsal opening 24 is provided in the body portion 12 within which the metatarsal insert 16 is received. The metatarsal opening 24 is arcuate, or “boomerang” shaped, and receives the metatarsal insert 16. An overhanging flange 26, or first step, is provided around the periphery of the metatarsal opening 24 and a second step 30 may be provided around the metatarsal opening 24 and adjacent to the overhanging flange 26, or first step. The cover 22 may have a cut-out portion aligned with the metatarsal opening 24.

The metatarsal insert 16 has a full thickness portion 34 comprising the portion that is inboard of the flange 26. The reduced thickness portion 36 of metatarsal insert 16 is received by the flange 26 and step 30. The reduced thickness portion may have one or two steps depending upon the configuration of the metatarsal opening 24. The reduced thickness portion 36 is bonded by an adhesive or solvent to the body portion 12 in the area of the first and second steps 26 and 30.

Referring to FIGS. 2 and 3, the insole 10 is shown as it appears after molding and trimming, but prior to assembly of the metatarsal insert 16. A fragmentary portion of the cover 22 is shown in FIG. 2. The cover 22 includes a plurality of vent holes 38 in the area located below a user's foot arch. The heel pod 18 is shown as it is secured to the body portion 12. A rear edge 40 of the heel portion is an arcuate area that conforms to the shape of the body portion 12 on the rear edge of the body portion. An arcuate groove 42 is provided between the front of the heel pod 18 and the portions of the body portion 12 located in front of the heel pod 18. A heel cup 44, as best shown in FIG. 3, is provided in the body portion above the heel pod 18. The heel cup 44 is concave in shape and curved to conform to the user's foot. A molded interface 46 is provided between the heel pod 18 and body portion 12. The heel pod 18 is initially formed by injecting elastomeric material into an injection mold to form the heel pod 18. Subsequently, the polyurethane and granulated cork mixture is injected into the mold. The polyurethane and cork mixture of the body portion 12 bonds to the heel pod 18 to secure the body portion 12 and heel pod 18 together.

Referring to FIGS. 4 and 5, the fully assembled insole 10 is shown. In FIG. 4, no arch support 20 is provided. In FIG. 5, a small arch support is shown assembled to the insole 10. Referring to FIG. 4, an arch support cavity 48 is shown between the metatarsal insert 16 and the heel pod 18.

Referring to FIGS. 6 and 7, two different sized arch supports 20 are shown. A small arch support 20′ is shown in FIG. 6 and a large arch support 20″ is shown in FIG. 7.

Referring to FIGS. 4-7, the arch supports 20′, 20″ have a convex upper surface 50 that is received in a face-to-face relationship in the arch support cavity 48. A plurality of transverse ribs 52 and a longitudinal rib 54 are formed on the convex upper surface 50. The ribs, 52 and 54, are received in an interference fit in a plurality of transverse grooves 56 and a longitudinal groove 58 formed in the arch support cavity 48. In the illustrated embodiment, the ribs are provided on the convex upper surface 50 of the arch support 20, but the ribs could be provided in the arch support cavity 48 with the grooves being provided in the convex upper surface 50 of the arch support 20. The ribs and grooves interlock to prevent the arch support 20 from shifting either in a lateral or a longitudinal direction. It should be understood that as used herein, the terms “lateral” and “longitudinal” are not to be construed in their strict directional sense, but indicate that they extend generally in the lateral or longitudinal direction, as illustrated. The arch support 20 may also be secured by means of an adhesive or glue to the arch support cavity 48, either with or without the intersecting ribs and grooves.

The process used to manufacture the insole 10 is an injection molding process that is performed using a clam shell type of injection mold. The clam shell injection mold includes an upper portion that defines an upper mold cavity and a lower portion that defines a lower mold cavity. The cover material fabric is pinned to the upper portion of the mold and spans the upper mold cavity. A sheet of thermo-formed plastic with embedded releasing agent is used to conform to the overall shape and defines the heel pod 18, arch area 48 and metatarsal opening 24 shape. The thermo-formed plastic with embedded releasing agent is inserted into the lower mold cavity of the lower portion of the mold. The thermo-formed plastic with embedded releasing agent is used to reduce tooling costs and increase mold life. The process could be performed without the use of the thermo-formed plastic form by molding directly on the lower mold cavity.

The injection mold is then closed and an elastomeric material that is preferably not foamed is injected into the heel pod forming portion of the thermo-formed plastic with embedded releasing agent or lower mold cavity. Next, the two-part polyurethane foam including 20% by weight granulated cork particles is blended and then injected into the mix head that mixes the material before injection into the mold. The mixture is injected into the lower mold cavity and onto the elastomer that was previously injected into the heel pod portion. The body composition mixture and elastomer of the heel pod are bonded together in the course of the molding process with a molded interface being created between the heel pod elastomer and the body mixture composition. The mold or thermo-formed plastic with embedded releasing agent sheet generally define the shape of the metatarsal opening during the molding process to reduce waste of the body mixture composition. The mold defines flange areas that extend about the metatarsal opening area 24. The flange area may have one or more steps 26, 30 to which the metatarsal insert is later adhered. The cover fabric is laminated to the top surface of the body portion 12 during the molding process.

After at least partially curing, the clam shell mold is opened and the body portion 12, heel cup 18, cover 22 and thermo-formed plastic with embedded releasing agent are removed from the mold. The metatarsal opening 24 is formed by cutting the molded body composition mixture and adhered cover fabric 22 in a die cutting operation. After the metatarsal opening 24 is formed in the body portion 12, the metatarsal insert 16 is assembled to the metatarsal opening 24 and bonded or otherwise adhered to the flange 26 that may also include the second step 30. The finished insert may be decorated with a heat transfer logo or the like.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. 

1. An insole for a shoe, comprising: a body that is configured to fit within the shoe, the body defining a heel recess that extends partially through the body in a heel area and a metatarsal opening that extends completely through the body in a metatarsal area; a heel insert secured in the heel recess; and a metatarsal insert secured in the metatarsal opening.
 2. The insole of claim 1 wherein the body has a hardness of between 25 and 35 on the Shore A scale and the inserts have a hardness of less than 10 on the shore A scale.
 3. The insole of claim 1 wherein the body has a hardness of 30 on the Shore A scale and the inserts have a hardness of 5 on the Shore A scale.
 4. The insole of claim 1 wherein the body is formed of a mixture of polyurethane and cork particles and the inserts are formed of medical grade silicone.
 5. The insole of claim 1 further comprising an arch support attachment that is assembled to a lower surface of the body between the heel area and the metatarsal area, wherein a rib is provided on one of the arch support attachment and the body and a groove is provided on the other of the arch support attachment and the body.
 6. The insole of claim 1 wherein the metatarsal opening is at least partially defined about the periphery of the metatarsal opening by a metatarsal opening wall extending from a top surface of the body to a bottom surface of the body and wherein the metatarsal insert is adhered to the metatarsal opening wall.
 7. The insole of claim 1 wherein the heel recess includes a heel area shoulder defined outboard of a base of the recess, wherein the shoulder has a depth that is less than the depth of the base.
 8. The insole of claim 1 wherein the metatarsal opening includes a metatarsal area shoulder defined outboard of the metatarsal opening, wherein the shoulder has a depth that is less than the thickness of the body in the metatarsal area.
 9. The insole of claim 8 wherein the metatarsal insert includes a step extending outwardly from the periphery of the metatarsal insert and configured to adhere to the metatarsal area shoulder.
 10. The insole of claim 1 wherein the heel recess extends from a bottom surface of the body and partially towards a top surface of the body.
 11. The insole of claim 1 wherein the shoe has an integral insole and the body is configured to fit within the shoe and on top of an integral insole.
 12. The insole of claim 1 wherein the shoe has an integral insole and the body is configured to fit within the shoe and to replace an integral insole.
 13. The insole of claim 1 further comprising a fabric layer that defines a cut-out portion and that is secured to the body with the cut-out portion being aligned with the metatarsal opening.
 14. The insole of claim 13 wherein the fabric layer includes a bamboo fiber.
 15. The insole of claim 13 wherein the fabric is adhered to a top surface of the body.
 16. An insole for a shoe, comprising: a body having a bottom surface and a top surface defining a thickness, the body defining: a heel recess extending from the bottom surface and partially towards the top surface in a heel area, and a metatarsal opening extending completely through the body in a metatarsal area, the metatarsal opening including a metatarsal shoulder defined outboard the opening that has a depth less than the thickness of the body; a heel insert secured to the heel recess; and a metatarsal insert secured to the metatarsal opening and metatarsal shoulder.
 17. The insole of claim 16 wherein the metatarsal insert includes a step extending outwardly from the metatarsal insert, the step providing a plurality of surfaces that face in at least two different directions, whereby the metatarsal insert is bonded to the metatarsal opening in multiple planes.
 18. A method of making an insole comprising: providing an injection mold; mixing a first part and a second part of a reactive resin system with a quantity of cork particles to form a body mixture; injecting the body mixture into the injection mold; molding a body portion of the insole to include a heel recess and a metatarsal opening area; molding a heel insert from silicone in the shape of the heel recess; molding a metatarsal insert from silicone in the shape of the metatarsal opening; providing the heel insert in the heel recess; and attaching a metatarsal insert to the metatarsal opening.
 19. The method of claim 18 wherein during the step of molding of the body portion, a base and a heel wall are formed about the heel recess and a metatarsal wall is formed about the metatarsal opening.
 20. The method of claim 19 wherein during the step of molding of the body portion, the heel insert is bonded to the base and the heel wall, and wherein during the step of attaching the metatarsal insert, the metatarsal insert is bonded to the metatarsal wall.
 21. The method of claim 18 wherein the injection mold has an upper portion that defines an upper mold cavity and a lower portion that defines a lower mold cavity, wherein the method further comprises attaching a segment of fabric to the upper mold cavity.
 22. The method of claim 21 wherein the method further comprises bonding the segment of fabric to a top surface of the body portion. 